Stabilized organic compositions



troit, Mich, assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 26, 1952, Serial No. 301,166

3 Claims. (CI. 44-69) This invention relates to the stabilization of organic materials normally susceptible todeterioration. More particularly, our invention relates to the inhibition of attack by oxygen and the prolongation of the-useful life of such materials.

Hydrocarbon fuels for use in internal combustion spark ignition engines may be classified broadly into three categories, according to the type of-engine for which they are manufactured and marketed, such as automotive, aircraft and diesel fuels. Although each type of fuel is composed essentially of hydrocarbons, the type and stability characteristics of the individual hydrocarbon types comprising each fuel differ considerably, as do the relative proportions of the various types in each 'fuel. For example, typical automotive :fuels contain straight and branched chain aliphatics, olefins, :naphthenesand some aromatics, typical aircraft fuels are particularly low in olefins and typical diesel fuels contain principally saturated hydrocarbons with a smaller proportion of olefins.

During the refining, manufacturing and blending processes, and during subsequent storage and handling operations, it is unavoidable that these fuels or their ingredients, such as cracked blending stocks, or the highly olefinic stocks for reforming and alkylation, are brought into contact with oxygen. The result of such contact is the formation, by oxidation or polymerization or a combination thereof, of gummy materials whichinterfere with the efficient utilization of said fuels in the engine.

Automotive ,ga'solines are, .in general, .more susceptible to this type of degradation by oxygen than aircraft fuels, while in recent years the degradation of fuels for -11sein compression ignition engines hasfbecome more significant. The presence of gummy materials in fuels for spark ignition engines causes Valve sticking, loweredspark plugefliciency, piston varnish and associated troubles, While such deteriorated fuels, when used in dieselengines, interfere with the operation of the 'fuel'filters and injectors.

Because of the specifications imposed on fuels .by the rigid requirements of present day. engines, particularly aircraft engines, it is "essential that any material capable of protecting such "fuels against deterioration be effective in extremely small quantities, on the order of one pound of additive per five ithous'an'd gallons of fuel, so that secondaryproblems do not arise ithroug'hthe'ir-use.

Many other materials in extensive use require proteo ti'on from the adverse e'fiects of contact with oxygen. One such class of materialsisthe e'la'stomers, both natural and synthetic. Upon absorption of oxygen .suchelastomers deteriorate prematurely, lose tensile strength and flexibility and "become discolored and embr itfled. Ibis absorption can occur during manufacturing operations, fabrication, storage or use. While certain materials have been proposed for "the protection of such elas'toiuer's from the deleterious action of oxygen, many of such protective substances possess the serious disadvantage, particularly with respect to light colored stocks, that the decomposition *products are themselves colored and hence interfere withthe color fastness of the stocks beingp'rotected.

nited States Patent 2,747,978 1e PatentedMay' m Further examples of materials which require protection from the effects of oxygen include mineral oils, lubricating oils, soaps, and diverse synthetic unsaturated-organic materials. In general, our invention is useful in protecting :those organic substances which, during the process of manufacturing, handling, (storage, or use, become exposed to and absorb oxygen with deleterious effects.

It is, therefore, an object of our invention to provide means for protecting such organic substances which deteriorate in or are affected adversely by oxygen. It is a further object of our invention to provide a class of substances which prevents the formation of gummy oxidation and polymerization products of unstable hydrocarbons in contact with oxygen. Another object of our invention is to provide means for stabilizing hydrocarbon fuels for internal combustion spark and compression ignition engines during the manufacturing, handling, and storage of such fuels prior to their use. A further object of our invention is to .provide hydrocarbon fuels containing tetraethyllead which do not deteriorate in contact withoxygen with the resultant formation of gum, and which do maintain for .long periods the qualities inherent in such finished fuelsat the time ofmanufacture. Likewise, itis an object of our invention to provide means for preventing embrittlement, discoloration, loss of tensile strength, and other harmful effects in elastomers during the milling, compounding, fabricating, storage, handling, and use ofsuch elastomer stocks. A further object of this invention is to provide means for protecting perishable material or synthetic organic materials from the adverse effects of contact with oxygen. Still further objects ofwour invention will appear from the description of our invention as hereinafter disclosed.

Throughout the history of the development of effective antioxidant compositions, recourse has been made to-compounds containing amine or hydroxy substituents on an aromatic nucleus. This can be substantiated by noting examples of the effective antioxidants used commercially to stabilize organic materials normally susceptible to deterioration. One of theearliest known antioxidants was comprised of mixed phenols from cracked wood :tar distillates. Other suchantioxidant materials contai-ningsaid substituents include ;N ,N-di sec-butyl-p phenylenediamine, N-n-butyl-p-aminophenol, 2,4-dimethyl-6-tert-butylphenol, hydro'quinone, aniline, tannic acid, .p-tolylhydroquinone, tert bu'tylhydroquinone, 4-methyl-2,6-di-t r utylphenol, 4,,6-di-tert-butylvmecresol, x-naphthyl-amine, fi-naphthyL amine, 'N,N'-di-n-butyl-pphenyIenediamine, N,N'.-t li-ispp'ropyl phenylenediamine, 2,Z methylene-bis- (4-metlr'y-l-6- tfirbbuty -pheuol), a mixed antioxidant cqmprising N,N'- di-sec-butyl-Pphehylenediamine and p-secmutylamino- Phenol, phy xynaph ho s, diamino rn p t lamines, the condensation product of butyraldehydeniline, aldol-a-naphthylaminfi, phenyLB-naphthylamine, and the like. However, we have made the startling discovery that the above and other objects of our invention can be ac complis'hed by employing sulfur-containing lead .canbamate, certain embodiments of which need not contain arylamine or arylhydroxy groups .to provide effective antioxidant materials.

In general, the antioxidants of our invention are characterize'd'by the structure radicals. In our preferred embodiments such R groups are aliphatic .or cycloaliphajtjic groups.

In naming certain of the embodiments of the sulfur- 3 containing lead carbamate of our invention, we prefer to utilize the term lead N,N,N',N'-tetraalkyl-dithiocarbamate, although it is recognized that these substances are also known by the term lead clialkyl-dithiocarbamate.

As will hereinafter be indicated, the compounds of our invention concurrently provide both primary antioxidant activity and synergistic effects to antioxidants of the arylamine type. This we believe is the noteworthy discovery inasmuch as, surprisingly, the lead cation of the class of compounds comprising the antioxidants of our invention in some currently unexplainable manner appears to be intrinsically involved in producing the overall antioxidant effectiveness.

The aliphatic radicals of the antioxidants of our invention can be saturated alkyl radicals such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-amyl, and the various positional isomers thereof as, for example, l-methyl-n-butyl, Z-methyl-n-butyl, 3 methyl n butyl, 1,1 dimethyl n propyl, 1,2 dimethyl 11 propyl, 2,2 dimethyl n propyl, and l-ethyl-n-propyl, and likewise the corresponding straight and branched chain isomers of hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octodecyl, nondecyl, eicosyl, and the like. In addition, these aliphatic radicals of the antioxidants of our invention may be unsaturated, containing double bonds, such as ethenyl, A -propenyl, n -propenyl, isopropenyl, A -butenyl, A -butenyl, A butenyl, and the corresponding branched chain isomers thereof as, for example, n -isobutenyl, A -isobutenyl, A -sec-butenyl, A -sec-buteny1, including l-methylene- A -propenyl, A -pentenyl, A -pentenyl, A -pentenyl, A pentenyl, and the corresponding branched chain isomers thereof, A -hexeny1, A -hexenyl, A -hexenyl, M-hexenyl, A -hexenyl, and the corresponding branched chain isomers thereof, including 3,3-dimethyl-A -butenyl; 2,3-di methyl-A -butenyl; 2,3-dimethyl-A -buteny1; 2,3-dimethyl- A -buteny1; and l-methyl-l-ethyl-A -propenyl; and similarly, the various isomers of heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octodecenyl, nondecenyl, eicosenyl, and the like.

In addition, the aliphatic radicals can be substituted. For example, when such substituents are aryl, our antioxidants contain aralkyl radicals such as benzyl; a-phenyl-ethyl, p-phenyl-ethyl, a-phenyl-n-propyl, p-phenyl-n-propyl, 'y phenyl -n -propyl, a phenyl isopropyl, 5 phenyl isopropyl, a phenyl n butyl, p -phenyl n butyl, y phenyl n butyl, 6 phenyl n butyl, oz phenyl isobutyl, ,8 phenyl isobutyl, 'y phenyl isobutyl, c phenyl sec butyl, 8 phenyl sec butyl, 'y phenyl sec butyl, ,3 phenyl t butyl, a naphthyl methyl, ,8 naphthyl methyl, or (oc' naphthyl) ethyl, a (,8 naphthyl) ethyl, p (0L, naphthyl) ethyl, p8 (13' naphthyl) ethyl, a (oz' naphthyl) n propyl, 0c 3' naphthyl) n propyl, fi (oc' naphthyl) n p py (1 p y n p py 'y naphthyl) n propyl, 'y (18' naphthyl) n propyl, a (a' napthyl) isopropyl, a (18 naphthyl) iso propyl, o: (a' naphthyl) n butyl, on naphthyl) n butyl, ,3 (06 naphthyl) n butyl, ,3 -(fi' naph thyl) n butyl, "y (cc' naphthyl) n butyl, v (,8 naphthyl) 11 butyl, 6 (oc' naphthyl) n butyl. 6 3' naphthyl) n butyl, a (oz' naphthyl) iso butyl, a 3 naphthyl) isobutyl, p3 (a' naphthyl) isobutyl, 5 (B' naphthyl) isobutyl, 'y (rx' naph thyl) isobutyl, V (5 naphthyl) isobutyl, a (a naphthyl) sec butyl, u (/3' naphthyl) sec butyl, fi (a' naphthyl) sec butyl, 8 (B' naphthyl) sec butyl, 'y (a' naphthyl) sec butyl, 'y ([3 naph thyl) sec butyl, )8 (oc' naphthyl) t butyl, B 8' naphthyl) t butyl, the corresponding a and 8 naphthyl derivatives of n-amyl and the various positional isomers thereof as, for example, said derivatives of 1 methyl n butyl, 2 methyl n butyl, 3 methyl n butyl, 1,1 dimethyl n propyl, 1,2 dimethyl n propyl, 2,2 dimethyl n propyl, l ethyl n propyl, and likewise said derivatives of the corresponding isomers of hexyl, heptyl, octyl, and the like including eicosyl. Other such aralkyl derivatives include the a', 8', and 'y' anthryl of alkyl radicals, such as, for example, or anthryl methyl, O6 (5' anthryl) ethyl, B anthryl) ethyl, or (0t anthryl) n butyl, 6 8 anthryl) 2 methyl n amyl, and the like, and corresponding alkyl derivatives of phenanthrene, fiuorene, acenaphthene, chrysene, pyrene, triphcnylene, naphthacene, and the like.

In addition, the aliphatic portion of such aralkyl radicals of the antioxidants of our invention can be unsaturated, containing double bonds such as tat-phenylethenyl, B-phenyl-ethenyl, a-phenyl-A -propenyl, [3-phenyl A propenyl, 'y phenyl A propenyl, a phenyl A propenyl, 8 phenyl A propenyl, 'y phenyl A propenyl, a phenyl isopropenyl, ,6 phenyl iso propenyl, 'y phenyl isopropenyl, and similarly, the phenyl derivatives of the isomers of butenyl, pentenyl, hexenyl, heptenyl, and the like, up to and including about eicosenyl. Other such arylalkenyls include a (a' naphthyl) ethenyl, 0c (,8' naphthyl) ethenyl, B (ot naphthyl) ethenyl, 5 ((i' naph thyl) ethenyl, 'cc (a' naphthyl) A propenyl, a 3 naphthyl) A propenyl, ,6 (a' naphthyl) A propenyl, [3 (,B' naphthyl) A propenyl, a (ec' naphthyl) A propenyl, a (/3' naphthyl) A pro penyl, 18 (a naphthyl) A propenyl, B (fl naph thyl) A propenyl, a (u' naphthyl) isopropenyl, a (,B naphthyl) isopropenyl, ,8 (OL' naphthyl) isopropenyl, B (fl' naphthyl) isopropenyl, and the like. In addition, such aromatic derivatives of alkenyls include derivatives of phenanthrene, fluorene, acenaphthene, chrysene, pyrene, triphenylene, naphthacene, and the like.

We also can employ as organic radicals in our antioxidants cycloaliphatic groups such as cyclopropyl, cyclobutyl, cycloamyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl, cyclo tridecyl, cyclotetradecyl, cyclopentadecyl, cyclohexadecyl, cycloheptadecyl, cyclooctodecyl, cyclonondecyl, cycloeicosyl, and such cycloaliphatic radicals as c-cyclopropylethyl, fl-cyclopropyl-ethyl, a-cyclobutyl-propyl, [i-cyclobutyl-propyl, -cyclobutyl-propyl, a-cycloamyl-isopropyl, fl-cycloamyl-isopropyl, and the like. Similarly, the cycloaliphatic groups comprise the cycloalkenyls such as acyclohexyl-ethenyl, fi-cyclohexyl-ethenyl, a-cycloheptyl- A -propenyl, fi-cycloheptyl-A -propenyl, 'y-cycloheptyl- A -propenyl, a-cyclooctyl-A -propenyl, fl-cyclooctyl-n propenyl, 'y-cyclooctyl-A -propenyl, fl-cyclononyl-isopropenyl, a-methylene-B-cyclododecyl-ethyl, and the like.

Thus, the organic radicals of our compounds contain from about 1 to 20 carbon atoms, are saturated or unsaturated, cyclic or acyclic, and the aforementioned can be substituted with at least one aryl group.

When each of X and X1 of the aforementioned generic structure is sulfur, there is provided a general class of lead dithiocarbamates. Therefore, specific examples of these compounds comprising preferred antioxidants of our invention include lead dithiocarbamate; lead N,N,- N',N-tetrarnethyl dithiocarbamate; lead N,N,N',N'- tetraethyl dithiocarbamate; lead N,N,N',N'-tetra-n-propyl dithiocarbamate; lead N,N,N',N-tetraisopropyl dithiocarbamate; lead N,N,N',N-tetra-n-butyl dithiocarbamate; lead N,N,N',N'-tetraisobutyl dithiocarbamate; lead N,N,N,N-tetra-sec-butyl dithiocarbamate; lead N,N,N,N-tetra-t-butyl dithiocarbamate; lead N,N,N,N- tetra-n-amyl dithiocarbamate; lead N,N,N',N-tetra-(lmethyl-n-butyl)-dithiocarbamate; lead N,N,N,N-tetra- (Z-methyl-n-butyl)-dithiocarbamate; lead N,N,N',N- tetra-(3-methyl-n-butyl)-dithiocarbamate; lead N,N,N,- N tetra (1,1 dimethyl n propyl) dithiocarbamate; lead N,N,N',N tetra 1,2 dimethyl n propyl):-

dithioc'arbaniate; lead N, N,N'.,N' -tetra- (2,2- dimethyl- 11 propyl) ditluocarbamate; lead N,N,N',N' tetra- (1 ethyl n propyl) diihiocarbarnate; and the like.

Similarly, our dithi'ocarbamate antioxidants comprise alkenyl substituted compounds providing, for example, such compounds as lead N,N,N',N'-tetraethenyl dithiocarbamate; lead N,N,N',N'-tetra-(A propenyl) dithiocarbamate; lead N,N,N,N'-te-tra-(A -propenyl) dithiocarbamate; lead N,N,N,N-tetra-isopropenyl dithiocarbamate; lead N,N,N',N'-tetra-(n -butenyl) dithiocarbamate; lead N,N,N',N-tetra-(A -butenyl) dithiocarbarnate; lead N,N,N,N-tetr'a-(A -butenyl) dithiocarbamate; lead N,N,N,N'-tetra-(A -isobutenyl) dithiocarbainate; lead N,N,N',N-tetra-(n -isobutenyl) dithiocarbamate; lead N,N,N',N-(n -sec-butenyl) dithiocarbamate; lead N,N,N,N'-tetra-(A -sec-butenyl) dithiocarbamate; and the like, including related compounds as, for example, lead N,N,N,N-tetra-(l-methylene-A propenyl) 'dithiocarbamate.

Furthermore, our dithiocarbamate antioxidants comprise aralkyl substituted compounds providing, for example, such compounds as lead N,N,N', '-tetra-(aphenyl-ethyl) dithiocarbamate; lead N,N,N',N'-tetra-(;3- phenylethyl) dithiocarbamate; lead N,N,N',N-tetra-(aphenyl-n-propyl) dithiocarbamate; lead N,N,N',N-tetra- '(fi-phenyl-n-propyl) dithiocarbamate; lead N,N,N',N'- tetra-(v-phenyl-n-propyl) dithiocarbamate; lead N,N,N'- N'-tetra-(a-phenylisopropyl) dithiocarbamate; lead N,- N,N,N-tetra-(ti-phenylisopropyl) dithiocarbamate; lead N,N,N',N tetra (a (a' naphthyl) n butyl) dithiocarbamate; lead N,N,N,N'-tetra-'(a-( 8-naphthyl)-n butyl) dithiocarbamate; lead N,N,N',N-tetra-(/3-(a'- naphthyl)-n-butyl) dithiocarbarnate; lead N,N,N,N'- tetra (,8 (B naphthyl) n butyl) dithiocarbamate; lead N,N,N',N' tetra (a (a tetrahydronaphthyl,)- isoamyl) dithiocarbamate; lead N,N,N ,N'-tetra-(fi-(u'- tetrahydronaphthyl) isoamyl) dithiocarbamate; lead N,N,N',N' tetra ('y (a tetrahydronaphthyl) isoamyl) dithiocarba-mate; lead N,'N,N',N tetra (6 (11'- tetrahydronaphthyl)-isoamyl) dithiocarbamate; lead N,- N,N.,N' tetra (c (5' tetrahydronaphthyl) isoamyl) dithiocarbamate; lead N,N,N',N'-tetra-(fl-(B-tetrahydronaphthyl)-isoamyl) dithiocarbamate; lead N,N,N',N'- tetra ("y 8' tetrahydronaphthyl) isoamyl) dithiocarbamate; lead N,N,N,N-tetra-(6-'(;8'-tetrahydronaph thyl)-isearnyl) di-thiocarbamate; and the like. Similarly, our dithiocarbamate antioxidants comprise aralkenyl substituted compounds providing, for example, such com pounds as lead N,N,N',N-tetra-(a-(d-anthryl)-A n pentenyl) dithiocarbarnate; lead N,N,N',N'-tetra-(a'-({i'- anthryD-A n-pentenyl) dithiocarbamate; lead N,N,N, N '-tetra--( e:- 'y-anthryl) -A -n-pentenyl) dithiocarbamate; lead N,N,N,N tetra (B e (0. phenanthryl) 1A npentenyl) dithiocarbamate; lead N,N,N,N'-tetra-('y-(;8'- phenanthryl)-A -n-pentenyl) dithiocarbamate; lead N,N,- N',N tetra (5 ('y' phenanthryl) A n pentenyl) dithiocarbamate; and the like.

Moreover, our dithiocarbamate antioxidants comprise cycloaliphatic substituted compounds providing, for example, such compounds as lead "N,N,N,N'-tetracyclopropyl dithiocarbamate; lead N,N,N',N-itetra-'(m-cyclobutyl)-amyl dithiocarbamate; lead N,N,N,N-tetra-(flcyclobutyD-isoamyl dithiocarbama'te; and the like. Similarly, cycloaliphatic derivatives of the alkenyls can be substituted in the dithiocarbamate antioxidants of our invention providing compounds such as, for-example, lead N,N,N,N tetra (a cycloheptyl) A propenyl dithioca'rbama'te; and the like.

Furthermore, R1, R2, R3, and R4 can be diiferent and be selected-from hydrogen and organic radicals providing as dithiocarbamate antioxidants of our invention such compounds as, for example, ilead N-methyl dithiocarbamateylead N,N*diethyl dithiocarbamate; lead N,N'- di-n propy l ilitliiocarbamate; lead N-methyl, N-isopropyl dithiocarbamate; lead N-n-butyl, N'-isoamyl dithiocar barnate; lead N,N,N'-triethenyl dithiocarbamate; lead N- ethyl, N -(A propenyl),N' (,8 phenyl) n propyl dithiocarbamate; lead N,N di sec butyLN' (on (Oi naphthyl) n propyl),N' (wcycloacmyl) A propenyl dithiocarbamate; lead N-methyl,N-ethyl,N'-n-propyl,N-n-butyl dithiocarbamate; and the like.

When X and X1 of the aforementioned generic structure are oxygen, there is provided a general class of lead thiocarbamates. Thus, specific non-limiting examples of these compounds comprising the antioxidants of our invention include lead N,N,N',N'-tetra-methyl thiocarbamate; lead N,N,N', '-tetra-ethenyl thiocarbamate; lead N,N,N',N'-tetra-(l-methyl-A -propenyl) thiocarbamate; lead N,N,N',N-'tetra-(u-phenylethyl) thiocarban-late; lead N,N,N',N-tetra-(u-(u'-anthryl)-A -hexenyl) thiocarbamate; lead N,N,N,N tetracyclopropyl thiocarbamate; lead N,N,N',N-tetr'a-(a-cycloheptyl)-A -propenyl thiocarbamate; lead N-methyl 'thiocarbama'te; lead N,N-diethyl thiocarbamate; lead N,N'-di-n-propyl-thiocarbamate; lead N-methyl, N-isopropyl thiocarbamate; lead N-n-butyl,N-isoamyl thiocarbamate; lead N,N,N- triethenyl thiocarbama'te; lead N-ethy'l, N-(A -propenyl),- N-(e-phenyl)-n-propyl thiocarbamate; lead N,N,-di-secbutyl,N (a (a naphthyl) n propyl).,N (a cyclm amyD-M-propenyl thiocarbamate; lead N-methyLN- ethyl, N-n-propyl,N'-n-butyl thiocarbamate; and the like.

Referring to the aforementioned generic structure, when X is oxygen and X1 is sulfur, there is provided a general class of mixed thio derivatives of lead carbamate comprising the antioxidants of our invention such as, for example, lead N,N-diethyl-t'hio (N',N'--diethyl-dithio) carbamate.

As shown above, R1, R2, R3, and R4 can be the same or dilferent and are selected from hydrogen or organic radicals. The selection of such radicals is contingent upon the solubility desired in the resulting compound. Thus, an antioxidant material for certain uses such as, for example, stabilizers for gasoline, diesel fuels, and lubricating oils, must exhibit relatively high solubility in hydrocarbons and an extremely low solubility in water to prevent extraction thereby. Likewise, a rubber antioxidant must possess certain compatibility and miscibility characteristics with the stock being protected. Similar considerations pertain for each class of substances for which our compounds are useful antioxidants.

In addition to our startling discovery that the aforementioned compounds provide efiective oxygen stabilization, we have discovered that these compounds have the property of greatly increasing the elfectiveness of previously known antioxidants of the arylamine type. Typical examples of these known arylamine antioxidants which are improvedby employing therewith such sulfurcontaining lead carbamates include N,N'-di-sec-butyl-pphenylenediamine; N :n butyl p aminophenol; N- isobutyl-p-aminophenol; N,N-cl.i-uanaphthylap-phenylenedia'mine; N,N' di isopropyl p phenylenediamine; N phenyl ,8 naphthylamine; 4 aminodiphenylamine; 2 aminodiphenylamine; and the like. Thus, 'Wehave found that the sultuncontaining lead carbamates can be employed both as primary antioxidants and as synergists.

The compounds of our invention are further defined by reference to the following method of preparation which, while not restricting the scope of the variations possible in different embodiments 'of "our invention, is representative of one method which we have employed in preparing the typical materials described herein. All quantities referred to herein are parts by weight.

LEAD N,N,N',N-TETRA-n-BUTYL- DITHIOCARBAMATE In a reaction vessel was placed 129 parts of dim-butylamine and 4001mm of water. To the resulting solution was added 90 parts of carbon disulfide over a period of one hour, maintaining the reaction mixture at a temperature of approximately C. The reaction mixture was then neutralized by adding thereto an approximately 10 normal sodium hydroxide solution using phenolphthalein as an indicator. The resulting solution was diluted to approximately 1,000 parts. One hundred parts of this solution was added to a solution of 19 parts of lead acetate and 100 parts of water. The resulting yellow curdy precipitate was filtered and dried. This crude lead N,N,N,N tetra n butyl dithiocarbamate was recrystallized from mixed hexanes, the resulting solid having a melting point of approximately 44 to 45 C. The product contained 33.46 per cent lead, while the empirical formula C13H36N2S4Pb requires 33.65 per cent lead.

The absorption of oxygen by hydrocarbon fuels can be measured directly by the standard method of the American Society of Testing Materials for determination of the oxidation stability of gasoline (Induction Period Method), ASTM designation: D52546, as fully described in part III-A, ASTM Standards for 1946. According to this method the induction period is the period during which there is no drop in pressure, indicating no absorption of oxygen when the test material is placed in a testing bomb maintained at a temperature of 100 C. with an initial pressure of 100 pounds per square inch gauge of oxygen. The induction period increase (IPI) is the increase in the duration of this period caused by the addition of a protective substance, and is adirect measure of the protection afiorded by such additive. Thus, the longer the IPI the more effective is the stabilizer. On the contrary, certain substances exert a prooxidant effect in which a negative IPI is obtained; that is, the duration of the induction period, or period of no absorption of oxygen, is less than in the absence of the additive.

As an example of the utility of sulfur-containing lead carbamates as primary antioxidants for various organic substances unstable to attack by oxygen, lead N,N,N',N-

tetra-n-butyl dithiocarbamate, also known as lead di-nbutyl dithiocarbamate, was prepared in accordance with the aforementioned procedure. To obtain the results shown herein alternately 3 milligrams and 6 milligrams of the additive were dissolved in 100 milliliters of a standard commercial gasoline, the properties of which are shown in Table I.

Table- 1 .PHYSICAL AND CHEMICAL PROPERTIES OF A TYPICAL COMMERCIAL GASOLINE Fully described in Petroleum Products and Lubricants, ASTM "Standards for 1951.

7 U. 0. P. Laboratory Test Methods for Petroleum and Its Products,

a Fully described in Petroleum Products and Lubricants, ASTM Standards prior to 1949.

Typical of the results obtained using the aforementijoned l nductio n Period Method, 3 milligrams of lead dip-aminophenol;

n-butyl dithiocarbamate per milliliters of gasoline produced an IPI of minutes, and 6 milligrams pro duced an IPI of 145 minutes. With another commercial gasoline of similar physical and chemical properties and having an Induction Period of 240 minutes, 3 milligrams of lead di-n-butyl dithiocarbamate per 100 milliliters of gasoline produced an IPI of 100 minutes, and 6 milligrams produced an IPI of 115 minutes. Similar results are obtained when other typical compounds of our invention are employed in concentrations of 3 milligrams and 6 milligrams per 100 milliliters of gasoline. Thus, for example, 3 milligrams of lead N,N,N,N-tetra-sec-butyl dithiocarbamate produced an IPI of 105 minutes, and 6 milligrams produced an IPI of minutes; 3 milligrams of lead N,N,N',N'-tetra-n-propyl dithiocarbamate produced an IPI of 120 minutes, and 6 milligrams produced an IPI of minutes; 3 milligrams of lead N,N,N',N'-tetra- \ethyl dithiocarbamate produced an IPI of 130 minutes, and 6 milligrams produced an IPI of 155 minutes; 3 milligrams of lead N,N,N,N'-tetraethyl dithiocarbamate produced an IPI of 110 minutes, and 6 milligrams produced an IPI of 130 minutes; 3 milligrams of lead N,N,N,N- tetraisopropyl dithiocarbamate produced an IPI of 115 minutes, and 6 milligrams produced an IPI of minutes; 3 milligrams of lead N,N,N',N-tetraisobutyl dithiocarbamate produced an IPI of 135 minutes, and 6 milligrams produced an IPI of minutes; and 3 milligrams of lead N,N,N,N-tetra-n-amyl dithiocarbamate produced an IPI of 130 minutes, and 6 milligrams produced an IPI of 150 minutes.

The compounds of our invention likewise provide protection to rubber stocks and the like. This can be determined by measuring the degree to which a test piece so compounded retains its elasticity after being subjected to accelerated aging according to the procedure of ASTM designation: D572-42 for a period of 96 hours at a temperature of 70 C. in the presence of oxygen pressure initially at 300 pounds per square inch gauge. By determining both the tensile strength and the ultimate elongation of such test pieces, it is found that our compounds greatly improve these properties of such rubber stocks.

As an example of the utility of our compounds concurrently providing both antioxidant activity and imparting a synergistic effect to antioxidants of the arylamine type, 3 milligrams of lead N,N,N,N-tetra-n-butyl dithiocarbamate and 3 milligrams of N,N'-di-sec-butyl-p-phenylenediamine were dissolved in 100 milliliters of a standard commercial gasoline having physical and chemical properties similar to those shown in Table I and having an Induction Period of 225. Alternately, 1.5 milligrams of lead di-n-butyl dithiocarbamate and 1.5 milligrams of N,N-di-sec-butyl-p-phenylenediamine were dissolved in 100 milliliters of a standard commercial gasoline. The results of these tests are shown in Table II.

Table II EFFECT ON INDUCTION PERIOD INCREASE 0F GASO- LINES Induction Period Increase, Minutes M t ib li ziil F s li N tG IX 1116 mg. lOlIl [1 111 e 3111 Mixgg gg Containing From ture Lead Mixture carbamate Similar results are obtained by the use of other species of our invention in combination with other arylamine antioxidants, as, for example, such mixtures as lead N,N,N',N-tetra-isobutyl dithiocarbamate and N-n-butyllead N,N,N,N'-tetra-isobutyl dithiocarbamate and N,N'-di-sec-butyl-p-phenylenediamine;

"9 lead N,N,N,N'-tetra-isobuty1 dithiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N'-tetra-isobutyl dithiocarbamate and N,N'-di-a-naphthyl-p-phenylenediamine; lead N,N,N,N-tetra-isobutyl dithiocarbamate and N,N-di-isopropyl-p-phenylenediamine; lead N,N,N',N- tetra-isobu-tyl dithiocarbarnate and N-phenyl-p-naphthylamine; lead N,N,N,N'-tetra-isobutyl dithiocarbamate and 4-aminodiphenylamine; lead N,N,N',N-tetra-isobutyl dithiocarbamate and lead N,N,N,N'-tetra-isobutyl dithiocarbamate and 2-aminodiphenylamine; lead N,N,N,N- tetra-t-butyl dithiocarbamate and N-n-butyl-p-aminophcnol; lead N,N,N,N'-tetra-t-butyl dithiocarbamate and N,N-di-sec-butyl-.p-phenylenediamine; lead N,N,N',N'- tetra-t-butyl dithiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N-tetra-t-butyl dithiocarbamate and N,N'-di-a-naphthyl-p-phenylenediamine; lead N,N,N',N- tetra-t-butyldithiocarbamate and N,N'-di-isopropyl-pph'enylenediamine; lead N,N,N',N-'tetra-t-butyl dithiocarbamate and N-phenyl-fi-naphthylamine; lead N,N,N',N-tetra-t-butyl dithiocarbamate and 4-aminodiphenylamine; lead N,N,N',N-tetra-t-butyl dithiocarbamate and Z-aminodiphenylamine; lead N,N,N,N-tetrasec-butyl dithiocarbamate and N,N-di-sec-butyl-p-phenyl enediamine; lead N,N,N,N'-tetra-sec-butyl dithiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N,N'- tetra-sec-butyl dithiocarbamate and N,N-di-a-naphthyl-pphenylenediamine; lead N,N,N',N'-tetra-sec-butyl dithiocarbamate and N,N-di-isopropyl-p-phenylenediamine; lead N,N,N,N'-tetra-sec-butyl dithiocarbamate and N- phenyl-{i-naphthylamine; lead N,N,N,N'-tetra-sec-butyl dithiocarbamate and 4-aminodiphenylamine; lead N,N,N',N'-tetra-sec-butyl dithiocarbamate and Z-aminodiphenylamine; lead N,N,N',N'-tetra-sec-butyl dithiocarbamate and N-n-butyl-p-aminophenol; lead N,N,N',N'- tetramethyl dithiocarbamate and N-n-butyl-p-aminophenol; lead N,N,N,N'-tetramethyl dithiocarbamate and N,N'-di-sec-butyl-p-phenylenediamine; lead N,N,N',N' tetramethyl dithiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N'-tetramethyl dithiocarbamate and N,N-di-a-naphthyl-p-phenylenediamine; lead N,N,N,N- tetraethyl dithiocarbamate and N,N-di-isopropyl-p-phen ylenediamine; lead N,N,N',N'-tetraethyl dithiocarbamate and N-phenyl-B-naphthylamine; lead N,N,N,N-tetraethyl dithiocarbamate and 4-aminodiphenylamine; lead N,N,N',N-tetraethyl dithiocarbamate and 2-amin0diphenylamine; lead N,N,N,N'-tetraisopropyl dithiocarbamate and N-n-butyl-p-aminophenol; lead N,N,N,N- tetraisopropyl dithiocarbamate and N,N'-di-sec-butyl-pphenylenenediamine; lead N,N,N',N-tetraisopropyl dithiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N'-tetraisopropyl dithiocarbamate and N,N'-diounaphthyl-p-phenylenediamine; lead N,N,N,N'-tetra-namyl di'thiocarbamate and N,N'-di-isopropyl-p-phenylenediamine; lead N,N,N,N-tetra-n-amyl dithiocarbamate and N-phenyl-p-naphthylamine; lead N,N,N',N-tetra-namyl dithiocarbamate and 4-aminodiphenylamine; lead N,N,N',N'-tetra-n-amyl dithiocarbamate and 2-aminodiphenylamine; lead N,N,N',N-tetra-n-butyl thiocarbamate and Nn-butyl-p-amino-phenol; lead N,N,N',N'-tetra-nbutyl thiocarbamate and N,N'-di-sec-butyl-p-phenylenediamine; lead N,N,N',N-tetra-n-butyl thiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N-tetra-n-butyl thiocarbamate and N,N-di-a-naphthyl-p-phenylenediamine; lead N,N,N',N-tetra-n-butyl thiocarbamate and N,N'-di-isopropyl-p-phenylenediamine; lead N,N,N',N- tetra-n-butyl thiocarbamate and N-phenyl-B-naphthylamine; lead N,N,N',N-tetra-n-butyl thiocarbamate and 4- aminodiphenylamine; lead N,N,N',N-tetra-n-butyl thiocarbamate and Z-aminodiphenylamine; lead N,N,N',N'- tetra-isobutylthiocarbamate and N-n-butyl-p-aminophe nol; lead N,N,N,N-tetra-isobuty1 thiocarbamate and N,N-di-sec-butyl-p-phenylenediamine; lead N,N,N,N'- tetra-isobutyl thiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N',N'-tetra-isobutyl thiocarbamate and N,N'-di-a-naphthyl-p-phenylenediamine; lead N,N,N',N-

tetra-isobutyl thiocarbamate and N,N'-di-isopropyl-pphenylenediamine; .lead N,N,N',N'-tetra-isobutyl thiocarbamate and N -phenyl -13 -naphthylamine; lead N,N,N',N-tetraisobutyl thiocarbamate and 4-aminodiphenylamine; lead N,N,N,N'-tetra-isobutyl thiocarbamate and Z-arninodiphenylamine; lead N,N,N,N-tetrat-butyl thiocarbamate and N-n-butyl-p-aminophenol; lead N,N,N,N'-tetra-t-butyl thiocarbamate and N,N'-di-secbutyl-p-phenylenediamine; lead N,N,N,N tetra-tbutyl thiocarbamate and N-isobutyl-p-aminophenol; lead N,N,N,N-tetra-t-butyl thiocarbamate and and N,N-dia-naphthyhp-phenylenediamine; lead N,N,N,N'-tetra-tbutyl thiocarbamate and N,N'di-isopropyl-p-phenylenediarnine; lead N,N,N',N-tetra-t-butyl thiocarbamate and N-phenylfi-naphthylamine; lead N,N,N',N'-tetra-t-butyl thiocarbamate and 4 aminodiphenylamine; lead N,N,N,N'-tetra-t-butyl thiocarbamate and 2-aminodiphenylamine; lead N,N,N,N'-tetra-sec-butyl thiocarbamate and N-n-butyl-p-arninophenol; lead N,N,N',N- tetra-sec-butyl thiocarbamate and N,N-di-sec-butyl-pphenylenediamine; lead N,N,N,N'-tetra-sec-butyl thiocarbamate and N isobutyl p aminophenol; lead N,N,N,N-tetra-secbutyl thiocarbarnate and N,N'-di-oc naphthyl-p-phenylenediamine; lead N,N,N',N-tetramethyl thiocarbamate and N,N'-di-isopropyl-p-phenylenediamine; lead N,N,N,N'-tetramethyl thiocarbamate and N-phenyl- ,B-naphthylamine; lead N,N,N,N-tetramethyl thiocarbamate and 4-aminodiphenylamine; lead N,N,N',N'-tetramethyl thiocarbamate and 2-aminodiphenylamine; lead N,N,N,N-tetraethyl thiocarbamate and N-n-butyl-paminophenol; lead N,N,N,N'-tetraethyl thiocarbamate and N,N di sec butyl p phenylenediamine; lead N,N,N',N-tetraethyl thiocarbamate and N-isobutyl-paminophenol; lead N,N,N',N'-tetraethyl thiocarbamate and N,N di 0c naphthyl p phenylenediamine; lead N,N,N,N-tetraisopropyl thiocarbamate and N,N-di isopropyl-p-phenylenediamine; lead N,N,N',N-tetrais0- propyl thiocarbamate and N-phenyl-a-naphthylamine; lead N,N,N,N-tetraisopropyl thiocarbamate and 4-aminodiphenylamine; lead N,N,N',N'-tetraisopropyl thiocarbamate and Z-aminodiphenyl-amine; lead N,N,N,N'-tetra-namyl thiocarbamate and N-n-butyl-p-aminophenol; lead N,N,N,N-tetra-n-amyl thiocarbamate and N,N'-di-secbutyl-p-phenylenediamine; lead N,N,N',N-tetra-n-amyl thiocarbamate and N isobutyl p aminophenol; lead N,N,N,N'-tetra-n-arnyl thiocarbamate and N,N'di-ocnaphthyl-p-phenylenediamine; and the like.

Mixtures of the sulfur-contaning lead carbamates of our invention when employed along with known arylamine antioxidants likewise provide protection to rubber stocks and the like. This can be determined by measuring the degree to which a test piece so compounded retains its elasticity after being subjected to accelerated aging accord ing to the above described procedure. By determining both the tensile strength and ultimate elongation of such test pieces, it is found that our antioxidant-synergist compositions greatly improve the functioning of aryl anti oxidants and overcome some of their inherent disadvan rages such as migration and bleeding.

The quantities of the compounds of our invention incorporated in the materials to be stabilized are not critical and depend largely upon the type of material being stabilized and the conditions under which the exposure to oxygen occurs. For example, with gasolines, diesel fuels, mineral oils, and similar materials, the compounds of our invention are preferably employed in concentrations between the limits of approximately 0.1 and 15 milligrams per milliliters of material to be stabilized. For other materials, such as, for example, soaps and natural and synthetic elastomers, somewhat larger amounts of the stabilizers of our invention are preferred and can be tolerated. Thus, in such materials we employ between approximately 0.1 and 2 parts of antioxidant per 100 parts of oxidizable material. Thus, our compounds can be satisfactorily employed in a wide range of concentrations,

.and we do not intend that our invention be restricted to the specific quantities mentioned herein.

We have disclosed a number of preferred embodiments of our invention and illustrated several means whereby protection can be afforded to organic materials sensitive to attack by oxygen. Our invention is not intended to be limited to the specific embodiments herein or to the means described herein for obtaining the advantages possible in employing our compounds, as other methods of practicing our invention will be apparent to those skilled in the art.

We claim:

1. A new composition stable to oxidation and consisting essentially of gasoline normally tending to deteriorate in the presence of oxygen and containing a synergistic antioxidant composition consisting essentially of substantially equal amounts by weight N,N'di-secbutyl-p-phenylene diamine and lead N,N,N,N-tetra-nbutyl dithiocarbamate, each being present Within the range of 0.1 to 15 milligrams per 100 milliliters of said gasoline.

2. Gasoline normally tending to deteriorate in the presence of oxygen and containing a synergistic antioxidant combination of N,N-di-sec-butyl-p-phenylene di- 12 amine and lead N,N,N,N '-tetra-n-buty1 dithiocarbamate, said phenylene diamine and said dithioearbamate each being present in said gasoline in an amount Within the range of 0.1 to 15 milligrams per 100 milliliters of said gasoline.

3. Gasoline normally tending to deteriorate in the presence of oxygen containing N,N-di-see-butyl-pphenylenediamine and lead N,N,N',N-tetra-n-butyl-dithiocarbamate, said phenylenediarnine and said dithiocarbamate each being present in said gasoline in amount equivalent to 3 rug/100 ml. of said gasoline.

UNITED STATES PATENTS References Cited in the file of this patent 2,016,648 Orelup Oct. 8, 1935 2,160,851 Faust June 6, 1939 2,356,661 Dawning et a1. Aug. 22, 1944 2,363,012 Miller et al Nov. 21, 1944 2,382,781 Dawning et al Aug. 14, 1945 2,395,382 Walters Feb. 19, 1946 2,400,106 Denison et a1. May 14, 1946 2,614,987 Dreher et a1. Oct. 21, 1952 

1. A NEW COMPOSITION STABLE TO OXIDATION AND CONSISTING ESSENTIALLY OF GASOLINE NORMALLY TENDING TO DETERIORATE IN THE PRESENCE OF OXYGEN AND CONTAINING A SYNERGISTIC ANTIOXIDANT COMPOSITION CONSISTING ESSENTIALLY OF SUBSTANTIALLY EQUAL AMOUNTS BY WEIGHT N,N''-DI-SECBUTYL-P-PHENYLENE DIAMINE AND LEAD N,N,N'',N'' TETRA-NBUTYL DITHIOCARBAMATE, EACH BEING PRESENT WITHIN THE RANGE OF 0.1 TO 15 MILLIGRAMS PER 100 MILLILITERS OF SAID GASOLINE. 